This invention relates to surface mounted packages for millimeter wave circuits.
There is growing demand for very compact, low-cost, millimeter wave communications and sensor circuits. In response to this demand, such circuits frequently use millimeter wave signal sources, which typically involve components and circuitry contained on dielectric (e.g., glass, plastic or ceramic) substrates.
At present, millimeter wave (mm-wave) signal sources are based on package designs that feature waveguide flange output ports or coaxial connector output ports. Such designs, however, are inappropriate for surface mounting. Surface mounting is desirable, for example, because it greatly simplifies manufacturing (e.g., components can be reflow solder attached to a circuit board or other substrate) and because it reduces the cost of the product and allows increased productivity.
Indeed, at present, no means are known to the present inventors by which a mm-wave signal source can be surface mounted to a printed-circuit board (PCB).
The above and other deficiencies in the prior art are addressed by the present invention. According to an embodiment of the invention, a surface-mountable mm-wave signal source is provided. The surface-mountable mm-wave signal source comprises:
(a) a conductive metal base;
(b) a mm-wave signal source disposed over an upper portion of the metal base;
(c) a first radio frequency transmission line carrying a quasi-transverse electric mode (xe2x80x9cquasi-TEMxe2x80x9d) signal from the mm-wave signal source, which is disposed over an upper portion of the metal base and proximate the signal source;
(d) a first mode transformer at least partially integrated into the upper portion of the metal base to convert the quasi-TEM signal carried by the planar transmission line into a rectangular waveguide mode signal;
(e) a waveguide well having upper and lower ends disposed within the base for carrying the rectangular waveguide mode signal from an upper portion of the base to a lower portion of the base; and
(f) a second mode transformer at least partially integrated into the lower portion of the base to convert the rectangular waveguide mode signal to a quasi-TEM signal within a second radio frequency transmission line.
The mm-wave signal source preferably operates in a frequency range of from 35 to 94 GHz, more preferably a frequency range of 70 to 80 GHz.
The mm-wave signal source, the first radio frequency transmission line and the mode transformer are preferably disposed within a metal cover over the upper portion of the base, which is preferably attached to the base by a solder or by a conductive adhesive.
At least one feed-through is typically provided, by which power or control signals can be transmitted between the lower portion of the base and the upper portion of the base. Preferably, the feed-through further comprises a conductive pin disposed within a dielectric insert, and the dielectric insert occupies a slot formed between the upper and lower portions of the base.
The mm-wave signal source, the first radio frequency transmission line (preferably a microstrip line) and at least portions of the first mode transformer are also preferably disposed on one or more dielectric substrates. The one or more dielectric substrates are typically attached to the base by a conductive epoxy.
Preferably, the first mode transformer comprises a glass substrate provided with a layer of patterned electrically conductive material and disposed over both (a) a shallow step region formed in an upper surface of the base and (b) the upper end of the waveguide well. The patterned electrically conductive material preferably comprises transforming fins for converting the quasi-TEM signal into the rectangular waveguide mode signal.
The second mode transformer preferably comprises an angled reflector and a tapered ridge transition. The angled reflector is disposed at the lower end of the waveguide well and reflects the waveguide mode signal onto the tapered ridge transition. The tapered ridge transition is shaped to convert the rectangular waveguide mode signal to a quasi-TEM signal within an adjacent microstrip line. The angled reflector and the tapered ridge transition are preferably integrated into the base.
The surface-mountable mm-wave signal source preferably includes a plurality of projections integrated into a lower surface of the base. In many preferred embodiments, at least one of these projections substantially surrounds the angled reflector and the tapered ridge transition.
Lower surfaces of the tapered ridge transition, the feed-throughs and the projections are preferably provided with a layer of solder, for ease of mounting.
The metal in the base of the surface mountable mm-wave signal source is preferably selected from (a) 85% tungsten/l 5% copper alloy, (b) 94% tungsten/2% nickel/2% iron/2% copper alloy, and (c) a stainless steel alloy. Although other fabrication techniques can be used, the base is preferably formed by metal injection molding.
According to another embodiment of the invention, a mm-wave electronic circuit is provided which comprises: (a) the above-described surface-mountable mm-wave signal source coupled to (b) a printed circuit board, which includes the above-noted second radio frequency transmission line. The second radio frequency transmission line is preferably a microstrip line formed on the printed circuit board.
The second mode transformer preferably comprises an angled reflector and a tapered ridge transition, wherein (a) the angled reflector is disposed at the lower end of the waveguide slot and reflects the rectangular waveguide mode signal to the tapered ridge transition, (b) the tapered ridge transition is coupled to the microstrip line formed on the printed circuit board, and (c) the tapered ridge transition acts to convert the rectangular waveguide mode signal into a quasi-TEM signal within the microstrip line formed on the printed circuit board.
The circuit board preferably comprises metallization for power and/or signal transmission and metallization for grounding and heat transfer. The metallization for power and/or signal transmission is coupled to the at least one feed-through and the metallization for grounding and heat transfer is coupled to at least portions of the base. Preferably, solder or conductive adhesive is used: (a) to couple the tapered ridge transition to the microstrip line formed on the printed circuit board, (b) to couple at least one feed-through to the metallization for power or signal transmission, and (c) to couple at least portions of the base to the metallization for grounding and heat transfer.
One advantage of the present invention is that a mm-wave source can be surface mounted to a printed circuit.
Another advantage of the present invention is that it greatly simplifies the manufacturing of the associated mm-wave PCB assembly.
These and other embodiments and advantages of the present invention will become immediately apparent to those of ordinary skill in the art upon review of the Detailed Description and Claims to follow.